1. Field of the Invention
The invention relates to a process for removing nitrogen from combustion flue gases.
2. Discussion of the Prior Art
It is known to feed ammonia to combustion flue gases for removing nitrogen (deNOxing), the nitrogen oxides reacting at a temperature of about 850.degree. C. with ammonia to form nitrogen and water. This process has the disadvantage that high deNOxing efficiencies entail a high ammonia slip. A further disadvantage is the relative high ammonia consumption.
German reference DE 36 34 360 C2 discloses a further process for deNOxing combustion flue gases, in which the flue gases are mixed with NH.sub.3, ammonia-containing substances, amines or amine-containing substances, and are then fed at a temperature of 150 to 600.degree. C. through at least one filter element which consists of a ceramic support material and has catalytically active substances that catalyze the reduction of nitrogen oxides. If the combustion flue gases are very highly polluted, which is for example the case with flue gases produced in the incineration of waste, this process can be used only if very short catalyst life is accepted. If operation is even possible, it is very costly. A further disadvantage of this process is that there is very substantial dioxin production because of the high catalyst surface temperature of up to 600.degree. C.